diff options
| -rw-r--r-- | drivers/md/dm-snap.c | 72 |
1 files changed, 26 insertions, 46 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 58c444fb189..c5449f2504b 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -851,7 +851,6 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, { struct exception *e; struct dm_snapshot *s = (struct dm_snapshot *) ti->private; - int copy_needed = 0; int r = 1; chunk_t chunk; struct pending_exception *pe = NULL; @@ -866,29 +865,28 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, if (unlikely(bio_barrier(bio))) return -EOPNOTSUPP; + /* FIXME: should only take write lock if we need + * to copy an exception */ + down_write(&s->lock); + + if (!s->valid) { + r = -EIO; + goto out_unlock; + } + + /* If the block is already remapped - use that, else remap it */ + e = lookup_exception(&s->complete, chunk); + if (e) { + remap_exception(s, e, bio); + goto out_unlock; + } + /* * Write to snapshot - higher level takes care of RW/RO * flags so we should only get this if we are * writeable. */ if (bio_rw(bio) == WRITE) { - - /* FIXME: should only take write lock if we need - * to copy an exception */ - down_write(&s->lock); - - if (!s->valid) { - r = -EIO; - goto out_unlock; - } - - /* If the block is already remapped - use that, else remap it */ - e = lookup_exception(&s->complete, chunk); - if (e) { - remap_exception(s, e, bio); - goto out_unlock; - } - pe = __find_pending_exception(s, bio); if (!pe) { __invalidate_snapshot(s, pe, -ENOMEM); @@ -899,45 +897,27 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, remap_exception(s, &pe->e, bio); bio_list_add(&pe->snapshot_bios, bio); + r = 0; + if (!pe->started) { /* this is protected by snap->lock */ pe->started = 1; - copy_needed = 1; - } - - r = 0; - - out_unlock: - up_write(&s->lock); - - if (copy_needed) + up_write(&s->lock); start_copy(pe); - } else { + goto out; + } + } else /* * FIXME: this read path scares me because we * always use the origin when we have a pending * exception. However I can't think of a * situation where this is wrong - ejt. */ + bio->bi_bdev = s->origin->bdev; - /* Do reads */ - down_read(&s->lock); - - if (!s->valid) { - up_read(&s->lock); - return -EIO; - } - - /* See if it it has been remapped */ - e = lookup_exception(&s->complete, chunk); - if (e) - remap_exception(s, e, bio); - else - bio->bi_bdev = s->origin->bdev; - - up_read(&s->lock); - } - + out_unlock: + up_write(&s->lock); + out: return r; } |